As the trend in semiconductors continues towards reduced critical dimensions, integrated circuits involving millions of transistors on a single chip have become commonplace. Due to the large number of devices on a single chip, an entire industry has evolved specifically to supply the semiconductor industry with software and hardware tools to automate much of the process of integrated circuit design.
Design automation tools are computer-based tools that assist through automation of procedures that would otherwise be performed manually. Simulation of proposed design functionality and synthesis of integrated circuit logic and layout are two examples.
An integrated circuit may implement logic functions that are a combination of various standard cells. A crucial step in completing the circuit design is typically a global routing step, which is an attempt to logically determine a path for each interconnection between cells in the entire design. Routing decisions are made based on the available avenues formed by the current placement of circuit elements and/or blocks, and are assigned in consideration of various costs, also referred to herein as constraints (e.g., to incur the shortest total length of interconnect lines between the connectors). Once the global router has assigned the general flow of interconnect lines, a detailed router attempts to make the interconnect lines fit the assignments made by the global router.
As more complicated designs are developed to achieve higher performance and higher reliability as well as efficient chip scaling, the demands placed on routing tools increase. It is therefore desirable to have improvements in routing for integrated circuit design.